Patch to add index length support

Fine! but I would replace this:

add_index(:accounts, [:name, :surname], :name => 'by_name_surname',
:limit => {:name => 10, :surname => 20})

by:

add_index(:accounts, {:name => 10, :surname => 20}, :name =>
'by_name_surname')

which also cover the first situation (with a simple index):

add_index(:accounts, :name => 10, :name => 'by_name')

With this, I don't think that the :limit option is really needed.

Hash doesn't preserve order, which is critical when declaring indices. Using limit parameter, I wanted to keep the syntax of the migrations when you specify a limit for a field.

Very good idea!

query_reviewer is always complaining about long indices in my apps, I guess this way I could solve this by defining shorter indices

This is a great idea. Anything that can help speed things up a little is wonderful.

+1

I'm posting +2 since it solve two problems, but you should also check #734. :)

Support to index length is really necessary. For example, let's suppose I want to slug a title. Since I don't want to index the whole title, I set it to 10 characters.

Nowadays, I have to execute SQL inside migrations. This would fix it, so +1.

But even if I say to myself "just add the index, forget the length", it wouldn't be possible because the title is probably bigger than the max index length in MySQL. This takes us to the second problem is solves:

If I insert an index with length inside my migrations using execute, when dumping the schema it dumps the index but not the length. So when I'm applying db:test:clone it will raise an SQL error, saying that the column can not be indexed because it's bigger than the max index length.

So +1 again.

I'm just doing this "essay", because Pratik refused the other ticket, which I hope not to happen again. :)

I updated the patch with schema dumper support, more tests and sqlite tests fixed.

Thanks for your comments.

+1, really nice patch

+1, very useful

+1, needed improvement.

+1 tests passing

+1, works as described and test pass.

+1, tests pass and create the indices as described

Good implementation, very userfull. Althought too much mysql dependent.

Please review the schema_statements.rb documentation between lines 262 and 278.

I see things like:

      #  add_index(:accounts, [:name, :surname], :name => 'by_name_surname', :limit => {:name => 10, :surname => 15})
      # generates
      #  CREATE INDEX by_name_surname ON accounts(name(10), surname(20))
      #  CREATE INDEX by_name_surname ON accounts(name(10), surname(15))

Regards

+1 this will be most welcome

Looks promising. However - am I right in thinking that mysql is the only database that handles index lengths?

Correct me if I'm wrong, but pretty much everything else in schema_statements is database-agnostic, right? Would it be feasible to push any of this patch into the mysql adapter? Failing that, we probably ought to at least note that :limit will only be supported on mysql.

Any chance this making into core now? :)

@jonathan this patch is only for mysql adapter, and only modifies the schema if you works with this adapter

I published a plugin with this feature for use while we wait the inclusion in the core.

http://github.com/eparreno/mysql_index_length/

I have to revise the patch to add more tests. In a few days I'll send a new patch.

OK, I'll take a look this week.

(from [5b95730edc33ee97f53da26a3868eb983305a771]) Add index length support for MySQL [#1852 state:resolved]

Example:

add_index(:accounts, :name, :name => 'by_name', :length => 10) => CREATE INDEX by_name ON accounts(name(10))

add_index(:accounts, [:name, :surname], :name => 'by_name_surname', :length => {:name => 10, :surname => 15}) => CREATE INDEX by_name_surname ON accounts(name(10), surname(15))

Signed-off-by: Pratik Naik pratiknaik@gmail.com
http://github.com/rails/rails/commit/5b95730edc33ee97f53da26a3868eb...

wooooow! so , now what's exactly the situation? I tried length indexes in 2-3-stable vanilla app and seems to work properly (I see you've changed :limit for :length)

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